A colleague of mine wanted a means to do something, so it was suggested that I write some software to do this. The software has turned into more than the original specification and is now something rather complex, however it is not fully functional still.

My colleague has not paid me anything so far and I am unwilling to continue writing the software until some faith has been reciprocated in my direction, as I have put a lot of effort into writing the software.

I am also unwilling to finish the software as I do not want to give away a huge chunk of my time and effort away as free, neither do I want to be under compensated for my efforts.

Some concerns I have. If I finish the software, what if the client doesn't pay me anything or pays too little, or what if I write the software to a usable level, but not complete and the client pays me a too little.

I have lost my motivation to finish the software, as more and more specifications have been added to the software and I have developed a substantially complex piece of software and been effectively paid nothing. To finish the software, I need motivation, money would do this, however the client doesn't want to pay for something that isn't complete, yet keeps adding more requirements.

I seem to be in a catch 22 with this, as I have developed some software on faith and have had no faith reciprocated in my direction.

I'm really not sure how to get some payment from the client or on how to develop a licencing model so that I get some money from the client and development resumes.